1. Field of the Invention
This invention relates to a door closer in which a recovering force is accumulated in a door closing direction at the time of opening a door and a braking force of a damper is performed at the time of closing the door and, more particularly, to a device for automatically closing a door by mounting a closer body having a function of a damper at the door and an upper frame through arms.
2. Description of the Prior Art
A conventional door closer consists, as shown in FIGS. 9 and 10 showing the using state of a door closer, of a closer body a, an arm c fixed at one end thereof to a piston driving shaft b of the door closer body a, and an adjusting arm g pivotally secured at one end thereof to the end of the arm c via a screw d, etc., and pivotally secured at the other end thereof to a mounting plate e via a screw f, etc.,
The door closer body a has a hydraulic cylinder (not shown) in a body case a', and a piston (not shown) telescopically inserted into the hydraulic cylinder through a return spring.
In order to use the door closer of the arrangement described above, the closer body a is clamped at the upper portion of a door j openably pivotally secured via a hinge i at the hanging side to a vertical frame h through one or more clamping screws k, and the mounting plate e is clamped at an upper frame l via one or more clamping screws (not shown). In this manner, the piston is telescopically driven against the return spring by the piston driving shaft b rotated by both the arms by the door opening operation, the recovering force is accumulated at the return spring, and the door j is so mounted as to be automatically closed by the accumulated recovering force accumulated at the return spring.
In the door closer described above, the closer body a and the mounting plate e are respectively mounted at the door j and the upper frame l in a door closing state. In this case, the door closer is so mounted that a recovering force of certain degree is accumulated at the return spring even at the time of closing the door by considering a latching in the door closing state.
However, according to the conventional door closer, a considerably large closer body a must be mounted in the vicinity of the upper frame l of the door j. Therefore, in case of a narrow mounting space like a glass engaging door, the door closer might be sometimes impossible to be mounted at the door.
Further, in order to fully open the door in a direction of an arrow m from the door closing state in FIG. 9, the piston driving shaft b must be rotated at a considerably large rotating angle by the arm c. Accordingly, the internal structure of the door closer body a must be so composed as to be allowed to be rotatable at the large angle. This considerably restricts the degree of freedom of the door closer body a in design.
In contrast, in view of the arm crossing angle .alpha. formed between the arm c and the adjusting arm g in FIG. 9, as the door is opened, the crossing angle .alpha. is gradually increased. When the door is fully opened, the crossing angle .alpha. is arrived at the maximum value. As a result, when a hand is released from the door j in the door fully opening state, the door j is closed by the recovering force accumulated at the return spring. If the door is intended to be held in a door opening state, another suitable stopper mechanism must be arranged.
The conventional door closer further has the following disadvantage. A closer body a and a mounting plate e are fixed directly to a door j and an upper frame l in a state that all components are assembled completely. At this time, since arms c and g are rotatably energized in a direction of an arrow m in FIG. 9 by the recovering force accumulated at a return spring, the mounting positioning and the mounting works of the closer body a and the mounting plate e are not so easy, but long time and labor are wasted.
In case of a repair when the closer body a is defective, an inspection and a maintenance of the closer body a, not only the closer body a but the mounting plate a must be removed. Therefore, when they are again mounted, there arise problems such as an alteration of mounting positions by considering insufficient strength of clamping of clamping screws due to looseness of holes to be again clamped with the screws, exposure of old screw holes to deteriorate a design feeling in external appearances of the door and the upper frame, etc.